Process for silver development of photopolymerization prints and print forming element therefor



Feb. 22, 1966 P. B. GILMAN, JR. ETAL 3,236,644 PROCESS FOR SILVER DEVELOPMENT OF PHOTOPOLYMERIZATION PRINTS AND PRINT FORMING ELEMENT THEREFOR Filed Aug. 6, 1962 PHOTOPOLYMERIZABLE LAYER //////j suPPoRT 1 PHOTOPOLYMERIZA BLE LAYER SUPPOPT UNEXPOSED SILVER HALIDE EMULSION LAYER PROCESSIN6 SOLUTION v SILVER BEARING POSITIVE IMAGE EXPOSED PHOTUPOLWER/ZABLE LAYER' 3,235,644 Patented Feb. 22, 1966 Free PROCESS FOR SlLVER DEVELOPMENT OF PHOTOPOLYMERIZATION PRENTS AND PRINT FORMING ELEMENT THEREFOR Paul B. Gilman, .lr., and Ralph W. Baxendale, Rochester,

N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New .lersey Filed Aug. 6, 1962, Ser. No. 215,079 14 Claims. (Cl. 96-29) This invention relates to imagewise photopolymerization of monomeric vinyl layers and particularly to a process for silver development of images obtained in said layers. Still more particularly the invention relates to a differential diffusion transfer process for silver development of photopolymerization images.

In the present invention, an imagewise-exposed photopolymerizable layer is developed to a silver-bearing print by the application of solubilized silver to the image portions thereof, usually by diffusion transfer from an unexposed silver halide emulsion layer. One aspect of the present invention is, therefore, somewhat related to a diffusion transfer process. In the usual prior art process of diffusion transfer, however, a print is formed in a nonlight-sensitive receiving layer by transfer and reduction of solubilized silver halide in the receiving layer from an exposed and developed silver halide emulsion layer which is in contact therewith. In such processes, in order that solubilized silver halide transfer only to those areas in the receiving layer which comprise the positive image areas, it is required that the negative-transferring emulsion layer be first exposed and treated with a photographic developing agent. In this way, the silver halide solvent affects only the unexposed silver halide and consequently, in the transfer process between the unexposed emulsion layer and the print receiving layer, the solubilized silver halide transfers essentially in those areas which yield the image areas of the final print. In processes of this type, it is sometimes difiicult to obtain a point of high resolving power due to lateral diffusion of the solubilized silver halide during the process of transfer to the receiving layer. By contrast, since the present invention selectively prints to an image in a polymeric, photo-exposed layer, the many difficulties of transferring solubilized silver halide in an imagewise manner to a non-light-sensitive layer are overcome.

An object of the present invention is to provide a process for preparing silver-image-bearing prints of good quality and stability. Another object is to provide a diffusion transfer process which employs a light-sensitive receiving layer and an unexposed silver halide emulsion layer. Still another object is to provide photopolymerizable elements for preparing positive silver-image-bearing prints. Other objects will become apparent from a reading of the specification and appended claims.

These and other objects of the present invention are accomplished by briefly contacting an imagewise-exposed, photopolymerized receiving layer containing silver precipitating nuclei with a physical developer, or with an unexposed silver halide emulsion layer in the presence of a solution comprising a photographic developer and a silver halide solvent. The photopolymerizable receiving layer, which generally becomes the print (usually positive) according to the invention, comprises a layer of photopolymerizable, ethylenically-unsaturated monomer containing a photocatalyst, such as cadmium sulfide, zinc sulfide, zinc oxide, etc., uniformly dispersed throughout the layer. The above photocatalysts also function as nuclei for physical development of the silver halide. Other photocatalysts can also be used even though they do not function as silver precipitating nuclei, but silver precipitating nuclei must then be added separately.

Where we refer herein to an ethylenically-unsaturated monomer, we mean those monomers having a light-sensitive or photopolymerizable CH=C group. Photopolyrnerizable monomers of this type are well known in the art and have been described in a number of domestic and foreign patents, for example, US. 2,289,540, issued July 14, 1942. See also Luckey and West U.S. Patent 3,038,800, issued June 12, 1962, and Baxendale and Luckey U.S. application Serial No. 71,141, filed November 23, 1960 for other examples of such monomers, and methods for preparing light-sensitive layers. According ly, suitable polymerizable compositions for use in preparing the photopolymerizable receiving layers of the inven tion include as the essential polymerizable component thereof, at least one polymerizable ethylenically-unsaturated vinyl or vinylidene compounds, for example, watersoluble acrylic monomers, such as acrylic acid, and derivatives of acrylic acid, e.g., methacrylic acid, methyl, ethyl, or propyl acrylate, etc., acrylamide, and derivatives of acrylamide, e.g., methacrylamide, methylene-bis-acrylamide, gamma dimethylamino-propylacrylamide, etc., metal acrylates, e.g., calcium acrylate; acrylonitrile, etc.; vinylpyrrolidone; vinylpyridines; quaternary salts of vinylpyridines, e.g., 1,2 dimethyl 4 vinylpyridinium methyl sulfate; etc. Of these monomers, acrylamide and metal acrylates, and derivatives of these monomers were found to be particularly suitable for producing homogenous mixtures with non-light sensitive, binding and vehicular substances, such as, for example, gelatin, zein, nylon, monostearin (glycerol monostearate), ethyl cellulose, polyvinyl pyrrolidone, maleopirnaric acid, methylmethacrylatemethacrylic acid copolymer, polymethacrylic acid, polyvinyl hydrogen phthalate, cellulose acetate phthalate, polyethylene glycols, such as Carbowax 4000 to Carbowax 20,000, etc. The numbers given the Carbowax materials indicate the approximate molecular weight.

The photographic elements and process of the invention are illustrated in the accompanying drawings wherein:

FIG. 1 shows an enlarged cross-sectional view of a light-sensitive printing element of the present invention comprising a support having a photopolymerizable layer superposed thereon.

FIG. 2 shows a process for exposing the light-sensitive printing element of FIG. 1 from behind a negative transparency to produce differentially polymerized areas in the photopolymerizable layer of said element.

FIG. 3 shows a process for producing positive silver images in the exposed photopolymerizable layer by diffusion transfer from an unexposed silver halide emulsion layer in the presence of a processing solution comprising a silver halide developing agent and a silver halide solvent. The photopolymerizable layer after exposure acts as a silver receiving layer in accordance with the invention.

Referring more particularly to the drawing, in FIG. 1, a support 10 is coated with a photopolymerizable layer comprising an ethylenically-unsaturated vinyl monomeric component 11 (e.g., acrylamide) which has uniformly 3 distributed therethrough a water-insoluble photocatalyst 12.

In FIG. 2 the light-sensitive element comprising a support having a photopolymerizable layer comprising the ethylenically-unsaturated monomeric component 11 and photocatalyst 12 is exposed through a negative trans parency having transparent areas 13 and opaque areas 14. The exposing source emits actinic radiations 15 from a light source 16 as intensified by a reflector 17.

In FIG. 3 the exposed light-sensitive element of FIG. 2 is placed in contact with an unexposed silver halide emulsion layer 19 carried on a support 18 in the presence of a processing solution 20 which comprises a silver halide developing agent and a silver halide solvent. According to the process as shown in FIG. 3, solubilized silver halide transfers by diffusion from the unexposed silver halide emulsion layer 19 to the exposed areas 21 of the lightsensitive element where the silver halide is reduced to metallic silver to form a positive silver image. Positive silver images can be produced in the light-sensitive photopolymerizable receiving layer simultaneously with the production of negative silver images in the unexposed silver halide emulsion layer, although the quality of the negative silver image is subject to considerable variation in quality, depending on amount of silver solvent present, etc.

In preparing the photopolymerizable receiving layers of the present invention, the photocatalyst (and also separate silver precipitating agent when the photocatalyst does not also function as a silver precipitating agent) is uniformly dispersed throughout a suitable polymerizable monomeric solution prior to coating on a suitable support. According to one feature of the invention, a solid photocatalyst for use in the photopolymerizable composition can be prepared under safelight conditions using a Kodak Safelight Filter, e.g., Wratten Series 1A, a process which comprises mixing, for example, an alkali metal sulfide with a suitable carrier, such as gelatin, followed by the addition of a Water-soluble salt of the photocatalyst cation, e.g., cadmium nitrate, with thorough mixing until precipitation of the photocatalyst sulfide is complete. The mixture is then uniformly dispersed in a solution of a polymerizable monomer, coated on a suitable support and dried. The photocatalyst that has been prepared and kept away from actinic radiation is called an unfogged catalyst.

Any of the metallic photocatalysts of the invention can be normally added in the coating compositions on preparation in an amount ranging from about 0.005 percent to about 10 percent by weight of the entire composition, with especially useful quantities being in the range from about 0.01 percent to about 1 percent. Of course, the optimum amount of photocatalyst will vary considerably, depending upon the chemistry of the particular compound.

When preparing the photopolymerizable compositions for use in the invention, it is usually necessary that the monomeric component be soluble in the solvent used, so that a homogeneous mixture can be prepared. A photocatalyst (and silver precipitating nuclei if needed) is then added to this mixture with agitation to assure uniform distribution of the photocatalyst throughout the medium. The monomeric component is usually present in the photopolymerizable compositions for preparing the silver re ceiving layer in an amount from about 10% to about 65% by weight of the total composition. The amount of solvent used in preparing a particular photopolymerizable composition is not critical, and the minimum amount need only be sufficient to permit a uniform coating. Amounts of solvent up to 90 percent and more of the entire solution can be used, although it is generally preferred that the amount of solvent not exceed 65 percent of this solution. If desired, only sufficient solvent to form a paste-like consistency need be used. To this solution, a vehicle or binder of choice (as indicated above) can be added in preparing the composition for coating on a suitable support. Although no binder need be contained in the polymerizing composition, it is often preferred to employ a binder to obtain improved physical characteristics. Suitable binder concentration can be in the range from about 5 percent to about 60 percent by weight of the total polymerizable composition. The preferred binder concentration is in the range from about 10 percent to about 30 percent by weight of the total composition. Compositions for use in the present invention should be prepared so that they can be dried to a firm nontacky layer. To assure suitable hardness in the dried coating, it is often advantageous to employ a suitable hardening agent, such as formaldehyde or mucochloric acid. Formaldehyde is particularly advantageous where gelatin is included in the receiving layer as a carrier. Compositions such as these can be readily coated, cast or extruded onto a suitable supporting material. Suitable supporting materials can include a wide variety of materials, such as paper (e.g., grease-proof paper, i.e., map overlay tracing parchment, glassine paper, vegetable parchment, etc.); cellulose film base (e.g., cellulose acetate, cellulose nitrate, cellulose acetate butyrate, cellulose acetate propionate, etc.); metals (e.g., aluminum foil); glass; etc. Other suitable materials comprise such synthetic materials as polyethylene, polypropylene, polystyrene, polyethylene, terephthalate, cellulose esters, and the like.

Light-sensitive receiving layers of the invention can also have incorporated therein auxiliary nucleating agents. While some of these agents alone do not appear to act as sensitizers for the photopolymerization, it was found that their use in conjunction with an inorganic catalyst for photopolymerization gave improved density in image areas after development. Nucleating agents of the type contemplated for such use can include any of the well known nucleating materials, such as those disclosed in Rott U.S. 2,352,014 and in Yutzy et al. U.S. 2,740,717. Suitable materials of the type described include sulfides of heavy metals, such as lead, silver, zinc, etc.; certain selenides; metals, such as silver, gold, platinum, palladium, mercury, colloidal silver; silver proteinate; and the like. Where an auxiliary nucleating agent is used together with an inorganic photocatalyst, or photocatalyst which has none or feebly silver nucleating properties, of the present invention, it can be mixed in the coating composition prior to coating on a support and stirred vigorously to assure uniform distribution throughout the medium. The concentration of the silver nucleating auxiliary agent in the coating composition can vary over a wide range. Normally, only a very small amount of such auxiliary agents is required to give optimum density improvements in the receiving layer. For example, receiving layers containing from about 0.002 gram of an auxiliary nucleating agent, such as colloidal silver, per ml. of coating composition Was found to give useful results in the present invention. The upper limit of concentration was not critical. However, most useful results can be obtained where the auxiliary agent is present in a range from about 0.002 gram to about 2.0 grams of agent per 100 ml. of coating composition.

When preparing the silver-receiving layer for producing silver images, the wet coating thickness of the compositions can vary widely. For example, a wet coating thickness of from about 0.0005-inch to about 0.0l5-inch was found to be suitable, with a preferred wet coating thickness in the range from about 0.002-inch to about 0.006- inch. Coating thicknesses within about this range were found to be easily dried and produced good silver images.

In accordance with a process of the present invention, the afore-described light-sensitive printing materials can be exposed to actinic radiation to form a latent image in the light-sensitive layers. The actinic radiation exposure is usually from behind a suitable negative or positive image having differential areas of transparency and opaqueness. Suitable source of actinic radiation can comprise such sources as a General Electric No. 2 reflector flood lamp or General Electric Osira lamps having two 400-watt high pressure mercury vapor tubes. Another suitable source of actinic radiation which emits radiations rich in ultraviolet comprises a 250-watt British Thompson-Houston type ME/D mercury arc. Where a radiation source of this latter type was used, a 500 mm. Bausch & Lomb Monochromator was placed between the illuminating source and the printing material. The light output was meas ured with a Weston photocell. This photocell was calibrated with a thermopile-galvanometer combination which had been standardized with Bureau of Standards lamps C52 and C-675. The preferred actinic radiation sources are those which give an exposure in the optimum range of sensitivity for the light-sensitive printing materials, which was found to be in the range from about 300 m to about 550 m l.

Following imagewise exposure of the lightsensitive photopolymerizable silver-receiving layer to a negative transparency to produce a latent image therein, either an unexposed and undeveloped silver halide emulsion layer comprising an emulsion such as silver chloride, silver bromide, silver chlorobrornide, silver bromoiodide, silver bromochloroiodide, etc., is placed in contact with the image-wise exposed receiving layer in the presence of a solution comprising a photographic developing agent and a silver halide solvent, or the photopolymerized layer is treated with a physical developer. After a brief interval, the exposed polymerized layer and the unexposed silver halide emul ion layer are separated and a positive silver image is obtained in the photopolymerizable layer and a usable negative silver image can be obtained in the unexposed emulsion layer. Following the diffusion transfer step, the print receiving layer can be treated in a number of ways, for example; further polymerized by over-all exposure to actinic radiation; developed by Washing away unexposed, unpolymerized portions with a suitable solvent; etc. Accordingly, the print receiving elements of the invention can be used in a number of processes Well known in the art.

In another process, a negative silver image can be produced in the receiving layer from a negative original (or a positive from a positive original). In this case, the solubilized silver halide is transferred by diffusion to, and reduced by, the unexposed areas of the receiving layer and deposited therein as metallic silver. In some cases, little, if any, transfer of solubilized silver halide occurs in the exposed areas of the print receiving layer. This process constitutes essentially a reversal process, since in this case a negative silver image is produced in the receiving layer from exposure to a negative or, on the other hand, a positive can be produced from a positive. In this latter process, a photopolymerizable composition, as hereinbefore described, is prepared into which is added a silver intensifying agent or toning agent such as certain organic mercapto compounds when employed alone, or in combination with a dithiabis quaternary ammonium salt of the type described in the copending application of P. B. Gilman et al., Ser. No. 141,036, entitled Photographic Silver Halide Diffusion Transfer Process, filed September 27, 1961, and now abandoned. Typical mercaptan compounds of this type include:

3-mercaptol,2,3a-triazaindene 3-mercapto-5-methyl-1,2,4-triazole 3-mercapto-1,2,4-triazo1e 4-phenylimino thiourazole 5-amino-2-mercapto-1,3 ,4thiadiazole 1-methyl-Z-mercaptoimidazole Suitable dithiabis quaternary ammonium salts comprise:

3,13-dithiapentadecane-1,15-bis-(N-methylpiperdiniump-toluene sulfonate) 3,8-ditl1iadecane-1,10-bis-(N-methylpiperdinium-ptoluene sul-fonate) 4,4,10,10-tetraoxo-4,10-dithiatridecane-bis-(pyridinium perchlorate) 3 ,1S-dithiaeicosane-1,20-bis-(N-methylpiperdinium-ptoluene sulfonate) 3 ,13-dithiapentadecane-1,15-bis-(N-methylmorpholiniurnp-toluene sulfonate) 3 ,14dithiahexadecane-1,16-bis-(dithiahexadecane-l,16- bis-(N-methylmorpholinium-p-toluene sulfonate) In preparing a photopolymerizable receiving layer for producing reversed silver images, i.e., forming the silver image in the unexposed areas of the receiving layer, a convenient procedure is to dissolve the silver intensifying agent (alone, or mixed with quaternary salt) in a suitable solvent, and add it with stirring to the photopolymerizable composition for coating on a support. The silver-intensifying agent can be added to the composition in an amount over a wide range. For example, from about 0.1 percent to about 5 percent by weight of the total weight of the coatable composition. The preferred amount is in the range from about 0.5 percent to about 2 percent by weight.

As indicated above, the essential constituents of the processing solutions for use of a diffusion transfer technique in the present invention comprise a photographic developing agent and a silver halide solvent. In such solutions suitable developing agents can comprise any of the well-known silver halide developing agents, such as Metol (e.g., N-methyl-p-aminophenolsulfate), hydroquinone compounds (e.g., hydroquinone, chlorohydroquinone, etc.), diaminophenols (e.g., 2,4-diaminophenol, 3,4-diaminophenolhydrochloride, etc.), glycine, l-phenyl- B-pyrazolidone, and its derivatives, triaminophenols (e.g., 2,4,6-triaminophenol), catechol, pyrogallol, gallic acid, p-phenylenediamine, ene-diols (e.g., ascorbic acid), and combinations of these developing agents.

The preferred silver halide solvents for use in the processing solutions of the present invention comprise alkali metal thiosulfates, such as sodium thiosulfate, potassium thiosulfate, etc., and ammonium thiosulfate. Thiocyanates can also be used as silver halide solvents.

The present invention will now be illustrated by reference to the following specific examples.

EXAMPLE 1 A light-sensitive photopolymerizable printing material was prepared as follows; the preparation and coating was gained out under Kodak Safelight Filter, Wratten Series To 275 ml. of a 0.4 percent gelatin solution were added 4 ml. of 0.25 molar sodium sulfide, followed by the addition with stirring of 100 ml. of 10 percent gelatin containing 4 ml. of 0.25 molar cadmium nitrate. To the mixture, while constantly agitating, were added 25 grams of acrylamide dissolved in 50 ml. methanol. To ml. of the mixture, while stirring, were then added 4 ml. of a 7.5 percent saponin solution and 3 ml. of a 10 percent formaldehyde solution. The final preparation was doctor-blade coated at a 0.002-inch wet thickness on a strip of cellulose acetate film base and dried overnight at room temperature. After drying, the above-coated strip was exposed for 2 minutes at l-foot through a line negative to a General Electric No. 2 photoflood lamp. The exposed printing material was then placed in contact with an unexposed silver bromoiodide emulsion layer which had been dipped in a processing solution of the composition of Table I to produce a positive silver image of good definition in the printing material corresponding to the image in the line negative. According to this example, metallic silver was deposited imagewise in the exposed, i.e., polymerized, areas of the photopolymerizable receiving layer.

7 Table I N-methyl-p-aminophenol sulfate "grams" 4 Hydroquinone do Sodium sulfite, anhydrous do 60 Sodium thiosulfate pentahydrate do 12 Sodium carbonate monohydrate do 50 0.5% carboxymethylcellulose ml 1000 Final pH adjusted to 11.0.

EXAMPLE 2 The image tone in Example 1 was somewhat brownish. A more neutral tone was obtained as follows:

To 85 ml. of the cadmium sulfide preparation of Example 1 Were added the following:

M1. 1% methanol solution of S-methyloxazoline-Z- thiol 0.5 1% methanol solution of 3-mercapto-1,2,4-triazole 1.0 1% aqueous solution of 4,4,10,10-tetra0x0-4,10-

dithiatridecane-bis(pyridinium perchlorate) 7.0

% methanol solutions of methylene-bis-acrylamide 10.0

The preparation was then coated at 0.002-inch thickness on a strip of vegetable parchment, dried at 125 F. and exposed as in Example 1. After exposure the printing material was contacted with an unexposed silver bromoiodide emulsion layer in the presence of a processing solution of Table 1.

After the one-minute contacting interval, the printing material was separated from the emulsion layer and a negative silver image was apparent in the printing material with a negative silver image being produced in the emulsion layer.

EXAMPLE 3 The following formula was coated at 0.003-inch wet thickness on glass and dried at room temperature.

Cadmium sulfide slurry (two parts water to one part cadmium sulfide by weight ml 100 Calcium acrylate grams 1.0

Carbowax 4000 do 2.0

The cadmium sulfide slurry was prepared by passing hydrogen sulfide gas with good stirring into a 2-liter volume of distilled water containing 57.1 grams of cadmium chloride until precipitation of cadmium sulfide was complete. The reaction was carried out under Kodak Safelight illumination using a Kodak Series 1A Wratten Filter. The cadmium sulfide precipitate was then washed five times by decantation with distilled water and the volume of the slurry made to 240 ml. The slurry was then stored in the dark until used.

The coating comprised of the above composition was exposed for one minute at a distance of 7 inches from a GB No. 2 reflector flood lamp from behind a line negative having transparent areas and opaque areas. After exposure, the coating was placed in contact with a silver chloride emulsion layer for one minute in the presence of a processing solution of Table II. After the contacting interval the light-sensitive printing material of this example was removed and a silver image of good definition was produced in the printing material.

Table II 4,4-dimethyl-l-phenyl-3-pyrazolidone gram 1.0 Hydoquinone do 10.0 Sodium thiosulfate pentahydrate do 10.0 Sodium carbonate monohydrate do 50.0 0.5% carboxymethyl cellulose ml 1000.0

pH adjusted to 11.0.

In a manner similar to that of the present example, comparable results were obtained where zinc sulfide was substituted for cadmium sulfide.

23 Similar results of this example were obtained using a photopolymerizable composition comprising cadmium sulfide dispersed in a solution containing a mixture of acrylonitrile and methylene-bis-acrylamide.

EXAMPLE 4 A zinc oxide-containing photopolymerizable receiving layer was prepared as follows.

To 20 ml. of a 10 percent gelatin solution were added 20 ml. of ethanol containing 10 grams acrylamide, 0.5 ml. of 10 percent formaldehyde solution, and 10 ml. of a 10 percent zinc oxide dispersion in 5 percent gelatin. The mixture was adequately stirred to uniformly distribute the zinc oxide, coated at 0.003 inch thickness on film support of titanium dioxide-pigmented, cellulose acetate, and dried.

The dried coating was exposed to a Kodak No. 2 Photoflood Lamp at 20 inches for 20 seconds and then placed in surface contact with an unexposed silver bromiodide emulsion which had been soaked for 3 seconds in a developer-solvent composition of Table III.

Table III Sodium sulfite, anhydrous grams 23 Potassium sulfite, anhydrous do 23 p-methylaminophenol sulfate do 6 Sodium thiosulfate pentahydrate do 7.7 Sodium Metaborate monohydrate do 46 Hydroquinone do 15 15 Molar ammonium hydroxide ml 10 Water to liter 1.0

After being in contact for about 30 seconds, the two layers, i.e., the unexposed emulsion layer and the receiving layer, were stripped apart revealing a positive image in the receiving layer corresponding to the exposed areas thereof with a substantially white background density in the unexposed areas.

The zinc oxide employed in the present example was French process zinc oxide sold as XX78 zinc oxide by the New Jersey Zinc Company.

EXAMPLE 5 A polymerizable receiving layer prepared as follows gave improved image quality.

To 20 ml. of a 10 percent gelatin solution were added 5 ml. of 5 percent aqueous gamma dimethylaminopropylacrylamide, 4 ml. of a 7 percent saponin solution, 3 ml. of a 2 percent chrome alum solution, 10 ml. of a cadmium sulfide dispersion in gelatin and 0.1 ml. of a 1 percent solution of aqueous methylene blue chloride. The CdS dispersion was prepared as in Example 1.

After suitable agitation to uniformly distribute the cadmium sulfide photocatalyst, the mixture Was coated in subdued illumination at 0.002 inch wet thickness on a titanium dioxide pigmented film support and dried. After drying, the light-sensitive photopolymerizable receiving layer was given an imagewise exposure as in Example 1 and placed in surface contact with a silver halide emulsion layer in the presence of a solution having the composition of Table III. After about 30 seconds contact time, the two layers were separated, revealing a positive silver image of low background density in the photopolymerizable receiving layer. The unhardened portions of the receiving layer could be removed by washing with tempered water or some other suitable solvent. Normally, however, the entire surface of the receiving layer can be permanently stabilized by exposure to light, thus rendering the entire surface hardened and containing a silver image after processing according to the example.

Similar improvement in background density was obtained using other dyes, for example, fiuorescein (disodium salt), etc.

9. EXAMPLE 6 A photopolymerizable receiving layer employing an auxiliary nucleating agent was prepared as follows.

100 ml. of an aqueous 1% gelatin solution containing 4 ml. of 0. 25 molar sodium sulfide were added to 200 ml. of distilled water followed by the addition to the mixture under safelight conditions of 100 ml. of distilled water containing 0.25 molar cadmium nitrate. After stirring for a brief interval, 10 ml. of the cadmium sulfide preparation were added to 20 ml. of a 10% aqueous gelatin solution to which was added the following:

(a) 20 ml. of an ethanol solution containing 10 grams acrylamide.

(b) 10 ml. of an ethanol solution containing 2 grams methylene-bis-acrylamide.

(c) 4 ml. of a 7 /2 aqueous saponin solution.

(d) 3 ml. of a 10% formaldehyde solution.

(e) 1 ml. of a silver protein solution prepared by dissolving 1 gram of silver protein in 1 liter of water containing 20 grams of gelatin. The silver protein was purchased from the Mallinckrodt Corporation.

Silver protein of the example can also be prepared from silver oxide and gelatin in the presence of alkali by heating the mixture until no precipitate is obtained upon the addition of a solution of silver chloride. This preparation when evaporated to dryness normally contains between '19% and 22% silver.

The composition of the example after thorough mixing was doctor-blade coated on a titanium dioxide pigmented film support at a wet thickness of 0.002 inch and dried.

The coating was then exposed to a line negative as in Example 1. The exposed coating was then placed in contact with an unexposed strip of fine grain negative speed silver halide emulsion which had been previously soaked in a composition of Table IV. After a contact time of about 90 seconds, a good visible image was obtained in the exposed coating and it was also noted that a good visible image was obtained in the contacting emulsion layer which was reversed with respect to the receiving layer due to the imagewise depletion of silver from the emulsion layer.

A second element was prepared in an identical manner as the one described above, except that the coating did not contain cadmium sulfide nuclei. In this case, no visible image was obtained in the exposed coating after contacting with a treated emulsion layer as hereinabove described.

Table IV p-Methylaminophenol sulfate grams 4.0 Sodium thiosulfate pentahydrate do 12.0 Hydroquinone do 5.0 Sodium carbonate monohydrate do 50.0 Sodium sulfite, anhydrous do 60.0 Carboxymethyl cellulose (0.5% solution) ml 1000.0 Arquad C 1 ml 40.0

1 Purchased from Armour and Co. and is a cationic qu at er nary ammoniumsalt of alkyltrimethyl ammonium chloride plus dialkyldimethyl ammonium chloride.

EXAMPLE 7 To 20 ml. of a 10% aqueous gelatin solution were added the follow-ing:

(a) 5 ml. of a 5% aqueous solution of 'y-dimethyl aminopropyl acrylamide.

(b) 4 ml. of a 7 /2 saponin solution.

(c) 3 ml. of a 2% potassium chrome alum solution.

(d) 8 ml. of a colloidal silver solution containing 0.001 gram of silver.

(e) 0.1 ml. of aqueous 1% solution of methylene blue chloride (used as photocatalyst).

The composition was then well mixed and coated on a suitable support at 0.002 inch wet thickness and dried. After drying, the coating was exposed and processed as in Example 6 to give a negative image of good quality. Instead of using methylene blue as a photocatalyst, other 10 photocatalysts, such as the azo-bis-alkane nitriles, ben- Zoin, etc., can be used. Acyloins of the type described in Crandall U.S. Patent 2,722,512, dated November 1, 1955, can also be used.

EXAMPLE 8 To 100 ml. of a 5% aqueous solution were added 20 ml. of cadmium sulfide dispersion prepared as described in Example -1, 5 ml. of 7.5% aqueous saponin solution, and 3 ml. of 10% aqueous formaldehyde. The dispersion was thoroughly mixed and coated at a thickness of .003 inch on ordinary acetate film support.

A second coating was made after adding 2 ml. of 50% aqueous .acrylamide to 10 ml. of the above mixture.

After drying, both coatings were exposed 20 seconds through a line image to a No. 2 photoflood lamp at a distance of 5 inches and then immersed in a physical developer prepared by adding a solution of 8 g. of silver nitrate in 50 ml. of distilled water to 30 g. of sodium sulfite in .150 ml. of distilled water until the white precipitate first formed disappears, diluting the mixture to 475 ml., adding g. of sodium thiosulfate and adding 0.25 g. of amidol per ml. of solution.

After both coatings were immersed in the physical developer for 5 minutes, the coating containing no acrylamide showed a uniform deposit of silver, while the coating containing acrylamide showed a positive reproduction of the line negative.

In another process, continuous tone positive prints were obtained from a silver negative where the negative was treated with a solution contain-ing a silver halide developing agent, a silver halide solvent, and a sulfur dioxide adduct, such as 2,2'-iminodiethanol -SO and then rolledin contact with a dry unexposed silver halide emulsion layer. A positive image was obtained in the emulsion layer, when it was fogged by light.

The advantages accruing as a result of the present invention are immediately apparent. Particularly advantageous is the production of visible silver images in differentially polymerized print-forming elements. Heretofore, light-sensitive polymerizable coatings have not been particularly adapted to produce visible prints since the visible changes between the polymerized and non-polymerized areas have not been particularly apparent, and certainly not sufiicient to produce a useful print. To produce any kind of a visible effect prior to the present invention, it has been necessary to create relief effects by wash development or transfer of unpolymerized portions of the ex posed element, or to expose supporting materials of contrasting colors, etc., by removal by wash means or otherwise the unpolymerized portions of a particular light-sensitI VE material. The present invention makes possible a single one-step process of development of a latent photographic polymer image in inexpensive print-forming materials which after development are stable, and usually unaffected by a variety of conditions, temperatures, humidities, etc., which so often have deleterious effects on final prints of many print-forming materials. It will also be apparent that the present invention is particularly adapted to producing improved direct-positive silver images employing a light-sensitive layer as the print-forming receiving layer.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the scope and spirit of the invention as hereinabove described and as defined in the appended claims.

We claim:

1. A process for producing silver images in the lightsensitive photopolymerizable receiving layer of a photographic element comprising (a) image-wise exposing to actinic light selected portions of said layer, and

(b) contacting said exposed layer with one of the following: (A) a photographic physical developer and (B) an unexposed silver halide emulsion layer in the presence of a processing solution comprising a silver halide photographic developing agent and a silver halide solvent, said element comprising a support and said receiving layer, said receiving layer comprising (1) an ethylenically-unsaturated, monomeric component having uniformly dispersed therethrough, (2) a composition selected from the class consisting of (C) a compound which is a catalyst for both photopolymerization of said monomeric component and physical development from said silver halide emulsion, and (D) a mixture of a catalyst for photopolymerization which is not a catalyst for physical development from silver halide and a catalyst for physical development from a silver halide emulsion which is not a catalyst of photopolymerization.

2. The process of claim 1 wherein said photopolymerization catalyst (C) is unfogged cadmium sulfide.

3. The process of claim 1 wherein said photopolymerization catalyst (C) is unfogged zinc sulfide.

4. The process of claim 1 wherein said photopolymerization catalyst (C) is Zinc oxide.

5. The process of claim 1 wherein said ethylenicallyunsaturated monomeric component is a water-soluble acrylic monomer.

6. The process of claim 1 wherein said receiving layer contains a binder for said monomeric component.

7. The process of claim 1 wherein said receiving layer contains a silver nucleating agent which is not a photopolymerization catalyst.

8. The process of claim 1 wherein said monomeric component is selected from the class comprising acrylamide, methacrylamide, methylene-bis-acrylamide and acrylic acid.

9. The process of claim 6 wherein said binder is selected from the class comprising gelatin, zein, nylon, monostearin, ethyl cellulose, polyvinylpyrrolidone, maleopimaric acid, and a polyethylene glycol having a molecular weight in the range from about 4,000 to about 20,000.

10. The process of claim 7 wherein said silver nucleating agent is colloidal silver.

11. A process for producing silver images in a lightsensitive photopolymerizable receiving layer of a photographic element comprising (a) exposing to actinic light selected portions of said layer and (b) contacting said exposed layer with an unexposed silver halide emulsion layer in the presence of a processing solution comprising a silver halide developing agent and a silver halide solvent, said element comprising a support and a receiving layer, said receiving layer comprising (1) an ethylenically-unsaturated, monomeric component having dispersed therethrough,

(2) a photocatalyst for photopolymerization of said monomeric component and nuclei for physical development of said silver halide emulsion.

12. A photographic print-forming element comprising a support having coated thereon a light-sensitive receiving composition comprising (a) an ethylenically-unsaturated, monomeric component having uniformly dispersed therethrough,

(b) a catalyst for photopolymerization of said monomeric component and for physical development from a silver halide emulsion and (c) a silver nucleating agent which is not a photopolymerization catalyst for said monomeric component.

13. A photographic print-forming element comprising a support having coated thereon a light-sensitive receiving composition comprising (a) an ethylenically-unsaturated, monomeric component having uniformly dispersed therethrough,

(b) a finely-divided water-insoluble, inorganic catalyst for photopolymerization of said monomeric component and for physical development from a silver halide emulsion and (c) a silver nucleating agent which is not a photopolymerization catalyst for said monomeric component.

14. A photographic print-forming element comprising a support having coated hereon a light-sensitive receiving composition comprising (a) an ethylenically-unsaturated, monomeric component having uniformly dispersed therethrough,

(b) an organic catalyst for photopolymerization of said monomeric component and for physical development from a silver halide emusion and (c) a silver nucleating agent which is not a photopolymerization catalyst for said monomeric component.

References Cited by the Examiner UNITED STATES PATENTS 3,019,104 1/1962 Oster 96 29 3,038,800 6/1962 Luckey et al 9635 3,041,172 6/1962 Evans et al. 3,050,390 8/1962 Levinos et al. 3,052,541 9/1962 Levinos 9627 3,060,022 10/1962 Duerr 9628 3,060,025 10/1962 Burg 9628 3,065,160 11/1962 Levinos. 3,075,907 1/1963 Levinos. 3,097,096 7/1963 Oster 9630 FOREIGN PATENTS 1,107,079 5/ 1961 Germany.

OTHER REFERENCES Mees: Theory of the Photographic Process, MacMillan, NY. (1954), pp. 74, 503, 504, 535-543.

NORMAN G. TORCHIN, Primary Examiner. 

1. A PROCESS FOR PRODUCING SILVER IMAGES IN THE LIGHTSENSITIVE PHOTOPOLYMERIZABLE RECEIVING LAYER OF A PHOTOGRAPHIC ELEMENT COMPRISING (A) IMAGE-WISE EXPOSING TO ACTINIC LIGHT SELECTED PORTIONS OF SAID LAYER, AND (B) CONTACTING SAID EXPOSED LAYER WITH ONE OF THE FOLLOWING: (A) A PHOTOGRAPHIC PHYSICAL DEVELOPER AND (B) AN UNEXPOSED SILVER HALIDE EMULSION LAYER IN THE PRESENCE OF A PROCESSING SOLUTION COMPRISING A SILVER HALIDE PHOTOGRAPHIC DEVELOPING AGENT AND A SILVER HALIDE SOLVENT, SAID ELEMENT COMPRISING A SUPPORT AND SAID RECEIVING LAYER, SAID RECEIVING LAYER COMPRISING (1) AN ETHYLENICALLY-UNSATURATED, MONOMERIC COMPONENT HAVING UNIFORMLY DISPERSED THERETHROUGH (2) A COMPOSITION SELECTED FROM THE CLASS CONSISING OF (C) A COMPOUND WHICH IS A CATALYST FOR BOTH PHOTOPOLYMERIZATION OF SAID MONOMERIC COMPONENT AND PHYSICAL DEVELOPMENT FROM SAID SILVER HALIDE EMULSION, AND (D) A MIXTURE OF CATALYST FOR PHOTOPOLYMERIZATION WHICH IS NOT A CATALYST FOR PHYSICAL DEVELOPMENT FROM SILVER HALIDE AND A CATALYST FOR PHYSICAL DEVELOPMENT FROM A SILVER HALIDE EMULSION WHICH IS NOT A CATALYST OF PHOTOPOLYMERIZATION.
 12. A PHOTOGRAPHIC PRINT-FORMING ELEMENT COMPRISING A SUPPORT HAVING COATED THEREON A LIGHT-SENSITIVE RECEIVING COMPOSITION COMPRISING (A) AN ETHYLENICALLY-UNSATURATED, MONOMERIC COMPONENT HAVING UNIFORMLY DISPERSED THERETHROUGH, (B) A CATALYST FOR PHOTOPOLYMERIZATION OF SAID MONOMERIC COMPONENT AND FOR PHYSICAL DEVELOPMENT FROM A SILVER HALIDE EMULSION AND (C) A SILVER NUCLEATING AGENT WHICH IS NOT A PHOTOPOLYMERIZATION CATALYST FOR SAID MONOMERIC COMPONENT. 